Stabilized chlorinated solvents and method of stabilizing such solvents



'use.

. methane,

Patented Oct. 26, 1937 STABILIZED CHLOBINATED SOLVEN'IS AND LIETHOD OFSTABILIZING SUCH SOL- VENTS Clarence F. Dinley, Detroit, Mich aslignorto James H. Bell, Philadelphia, Pa.

No Drawing.

11 Claims.

My invention relates to volatile chlorinated solvents and theirpurification, stabilization, and

Such solvents are exemplified by trichlorotetrachloromethane,dichlorethane, tetrachlorethane, trichlorethylene, andtetrachlorethylene. An object'of the invention isto prevent corrosion orother such action on metals exposed to such solvents,--even when thesolvents are heated and vaporized, and are exposed to the air orotherwise inv contact with moisture. Such corrosion may arise in thecleaning of metal parts with chlorinated solvents, and in the use ofsuch substances in metallic apparatus,for cleaning or for otherpurposes. The use of such solvents as cleaning and degreasing agents hasbeen widely attempted, since they are well known as solvents for oil andother grease. This application is a divisional continuation in part ofmy copending application Serial No.'566,1'76, filed September 30, 1931,as to common subject matter.

In the cleaning processes just referred to, metallic or other objects tobe cleaned are introduced into a vessel or apparatus containing theheated solvent and its vapor, and constantly or intermittently open (orpartly so) to permit the easy introduction and withdrawal of the work.This is possible without excessive loss of solvent vapor because thelatter is heavier than air, and because provisions are made to condensethe solvent vapor and prevent its escape. Sometimes contact or treatmentwith the hot liquid solvent is mainly relied on to clean or degrease theob- Ject(s) or work; sometimes treatment with the solvent vapor; andsometimes both.

While chlorinated solvents have been found of great value for these andother purposes, their use has been attended with serious drawbacks.Metal articles cleaned with such solvents are subject to objectionablespotting, while metallic apparatus in which the solvents are used issubject to progressive corrosion, that greatly abbreviates its usefullife. Also, dangerous fumes are given off, that injuriously affectworkers and may even render the vicinity of the apparatus uninhabitable.However, I have discovered ways of obviating such drawbacks.

I have found, in the first place, that these drawbacks are not due toany action of the chlorinated solvents themselves, but to chlorine(present as impurity in the solvent) in available reactive forms, suchas hydrochloric acid or other' chlorine acids, and free chlorine, even.Commercial chlorinated solvents commonly contain such availablechlorine. and may have an acidity Application March 5, 1935, Serial No.9,447

that is of measurable magnitude. Moreover, exposure of the (hot) solventto the atmosphere in the partly open apparatus results in decompositionyielding available chlorine and/or acid, by reaction of the solvent withthe atmospheric moisture, and with water that finds its way into theapparatus.

I have further found that in practice such troubles can be overcome bypreparing the solvent or carrying out the treatment with it in suitableways-preferably both. One way of doing this is to carry out thetreatment with the solvent in the presence of a reagent that willneutralize or eliminate the available acid and chlorine, such as analkali or an alkaline metal or compound that is readilychlorinatable,-and preferably water-insoluble or nearly so. Watersoluble alkalis have the general drawback that any excess alkali mayprove as detrimental as the acid that is to be neutralized. Because oftheir cheapness, various forms of calcium carbonate are commerciallypreferable, such as broken or crushed limestone or marble. However, manyother substances are known to chemists as having suitable properties,including alkaline earth and other metal oxides and carbonates, such asmagnesium oxide or carbonate, cadmium oxide, zinc oxide or carbonate,etc.

While such substances as indicated above perform their function verywell in the liquid solvent, their influence is not felt in the vapor ofthe solvent; and it is especially in the vapor phase that the solventdecomposes, and that acid and (free) available chlorine are formed. Bestresults are obtained, therefore, by carrying out the treatment in thepresence of a reagent that is of such volatility as to vaporize with thesolvent, and that will stabilize the solvent vapor or counteract theobjectionable decomposition, whether by being itself readilychlorinated, or' by neutralizing deleterious products formed in thevapor, or by preventing the usual decomposition of the solvent (i. e.,stabilization in a stricter sense). Whatever its action, the agentemployed should, of course, be compatible with the undecomposed solvent,so as neither to react with it under the conditions of use, nor to bedriven off or separate from the solvent. That it should not boil so muchbelow the solvent as to be driven off by the heat is also implied in itscompatibility with the solvent, as well as in the statement that itvaporizes with the solvent. This last statement also implies, of course,that the stabilizer volatilizes without being itself decomposed by theheat. A great many organic substances such as hereinafter indicated areknown to chemistsas having suitable properties. I

Examples of .the class that are efiective, as

I believe, by neutralizing the (chlorine) acid, as

well as by undergolng'chlorination, are the volatile organic bases suchas amines. characterized by the radical, and pyridine and the like. I

I characterized by the nitrogenzradical.which.in

the case of pyridine is included in the ring. They are soluble. inchlorinated solvents, and impart to theproduct an alkaline reactionwhen-used" in sufficient: proportions,such as those hereinafterindicated: I The alkaloids such as caffeine,

quinine, etc.,-are in general not sufliciently vola-' tile for thepurposes of my composition as now claimed herein. I

- Examples-oi; another class are eamphor. and I s so;

I pyridine,

I pyridine.

moisture.

prevent or obviatez trouble from the usual decomposition of the solventinc-the presence of They are generally soluble in trichl'orethylene andI other: chlorinated solvents, and steam-distiL- as: against theiradvantages of volatilizing I readily and stabilizing solvents veryeffectively,

ized i by exceedingly unpleasant odors.

in particular, which is relatively inexpensive, has a very objectionableodor. compensatively, the essential oil class of stabilizers havedecided but i'nofiensive; odors. 'They. are more; costly than such ashereinafter referred to in connection with It is the class ofstabilizers represented by the essential oils in general (and speciallycamphor and turpentine) that I aim to cover in thisapplication,-including especially their use together with volatileorganic base stabilizers, or even with less volatile or non-volatilealkaloids, or with both organic bases and alkaloids, as well as bythemselves. I also aim to cover more specially the combined use ofessential oils and the organic base type or class of stabilizers,consisting essentially of amines and basic cyclic organic compoundscharacterized by nitrogen in the ring,of which latter the pyridines areprominent examples.- g as a stabilizer for the solvent. Ido not,however, herein claim stabilization by alkaloids per se, which iscovered by my copending application Serial No. 725,732, flled May 15,1934. Nor do I herein claim stabilization by organic bases per se, orthe generic invention involved in the use of volatile organicstabilizers in general for my purpose, since these are covered by myapplication Serial No. 566,176 filed September 30, 1931, whereof thisapplication is a continuation in-part.

In so far as the essential oil or other stabilizing agents (whethervolatile or not) are actually chlorinated by chlorine (acid) liberatedby incipient decomposition of the solvent, or neutralize such acid, thisremoval of a product of decomposition seems one probable rationale ofthe stabilizing effect. This applies equally to chlorination ofthesolvent in the strict sense, involving insertion or substitution ofchlorine in the stabilizer molecule, or its addition thereto, and toandnot so readily volatilized-,-al-' though the water commonly presentwith chlori- I i hated solvents assists somewhat in. their volatil- Iization. Besides masking offensive odors, the use of essential oilsalong with organic basesin stat bilizingsolvents obviates the metaltarnishing I sometimes produced. by organic: bases alone -wchlorinatlonzlnvo lv lng addition of chlorine acid '(HCl) to thestabilizer molecule, to form a hydrochloride. both types ;ofchlorination. (e. g., turpentine);

I some only of the first type (e. g., camphor) and latter is exposed tothe atmosphere.

together are not: limited to the masking of odors the like. Insofar asthe essential oil inhibits de.

and insofar as the essential oil inhibits corro- :sion' of: metal bysuch chlorine acid, it reinforces the stabilizing action of I theorganic base in pro-:--

tecting the metal. Similar observations apply Some essential oils aresusceptible of withithe hotsolvent or its vapor, even when the 1 Itwould appear that the advantages of using essential oil and organic baseor other stabilizers;

:or the preventionoftarnishing, as by yr dm ml I 2Z5 Q the organic basesas'a'cla'ss are Often. character 1 0 the use of essen i i h alkaloids,all I Pyridine; I three types of stabilizers togethen; is some- I whatanalogous to the fact-that certaln'drugs taken; concurrently produce amultiplied effectrather than a merely cumulative one. 1 I

stone may; be put into the. pools of liquid in the apparatus whereobjects are treated with solvent, and these deposits replenished fromtime to time, so as to assure an ample supply at all times; and theorganic stabilizer may be added to the liquid solvent in the apparatusbefore it has been materially heated,as soon as the marble or limestonehas had a chance to free the solvent of its initial acid or the like.Instead, however, of treating and stabilizing the solventin theapparatus where objects are treated therewith, it is preferable to dothis beforehand.

In general, the proportion of the organic agent added to the solvent maybe anywhere from about of 1% to about 1 by weight. However, largerproportions may sometimes be used: e. g., A to 5% of pyridine, which hasno effect on steel; although in excess it will slightly tarnish highlypolished brass. Such proportions of organic stabilizer .suflice tomaintain an admixture thereof with the heated chlorinated solvent notmerely during one ordinary treatment of work with the solvent, but overan extended period of use of the solvent, involving manysuch'treatments.

Such, purified and stabilized chlorinated solvents are useful for manypurposes besides the cleaning processes herelnbefore referred to, and

will not cause corrosion or give off objectionable fumes as long as anyof the stabilizing ingredient remains. In using such prepared solvent inthe cleaning processes above indicated, its stability may be prolongedby the presence of marble or limestone in the apparatus, as explainedabove, and may be extended indefinitely by repeated timely additions ofthe stabilizing agent.

The boiling points of volatile aliphatic chlorin- I As theorganicstabilizers are comparatively expensive. it may be'desirable to use themuch less expensive solid alkalis like. marble or limestone in 1conjunction with them, to take care of (chlorine) acid; or otherformsofavailable chlorine existing or; produced-in the liquid solvent. Forthis'pur I I pose, several handfulsof broken marble or; lime I ated solventsand of specific stabilizers hereinbefore mentioned are as follows:

Accordingly, I have limited certain of my claims to aliphatic (or other)chlorinated solvents bolling under substantially 150 C., together withsuitably correlated stabilizers. To express more definite correlation ofthe stabilizer with the solvent, I have in certain claims referred tothe boiling point of the stabilizer as sufliciently near that of thesolvent to insure vaporization of the stabilizer concurrently with theboiling of the solvent ln substantial proportions, under the influenceof heat,as contrasted with the minute proportions (less than of 1%) inwhich substances boiling at temperatures very much higher than thesolvent (e. g., aniline as compared with trichlorethylene) wouldvaporize with the boiling solvent.

Having thus described my invention, I claim:

1. An improved process of treating greasy objects with hot volatileorganic chlorinated grease solvents that decompose when exposed in thehot vapor state to the atmosphere or to moisture, with generation ofchlorine acid, and of preventing the decomposition of the solvent,notwithstanding such exposure; which process comprises heating andvolatilizing, along with the organic chlorinated solvent that is exposedto the atmosphere or to moisture, stabilizing essential oil that iscompatible with the moist chlorinated solvent, volatilizing with itwithout being decomposed by heat but not boiling off from it below theboiling point of said solvent; and treating the objects with the solventthus stabilized, while maintaining admixture of volatilized essentialoil with the chlorinated solvent vapor during the exposure of thesolvent to the atmosphere or to moisture.

2. An improved process of treating greasy objects with hot volatileorganic chlorinated grease solvents that decompose when exposed in thehot vapor state to the atmosphere or to moisture, with generation ofchlorine acid, and of preventing the decomposition of the solvent,notwithstanding such exposure; which process comprises heating andvaporizing, along with the organic chlorinated solvent that is exposedto the atmosphere or to moisture, stabilizing essential oil and organicbase that are compatible with the moist chlorinated solvent, vaporizingwith it without being decomposed by heat but not boiling ofi from itbelow the boiling point of said solvent; and treating the objects withthe solvent thus stabilized, while maintaining admixture of vaporizedessential oil and organic base with the chlorinated solvent vapor duringthe exposure of the solvent to the atmosphere or to moisture.

3. An improved process in accordance with claim 2 wherein the organicbase is a volatile am ne base characterized by the nitrogen radical.

4. An improved process in accordance with claim 2 wherein the organicbase is a'volatile basic cyclic organic compound characterized bynitrogen in the ring.

5. An improved process of treating greasy objects with hot volatileorganic chlorinated grease solvents that decompose when exposed in thehot vapor state to the atmosphere or to moisture, and of preventingcorrosion of metal par-ts, whether of the apparatus used or the objectsbeing treated, that come in contact with such hot liquid or vaporoussolvent, notwithstanding the exposure 01 the solvent; which processcomprises heating and vaporizing, along with the organic chlorinatedsolvent that is exposed to the atmosphere or to moisture, stabilizingessential oil that is compatible with said chlorinated solvent,vaporizing with it without being decomposed by heat but not boiling oflfrom it below the boiling point of said solvent; and treating theobjects with the solvent thus stabilized, while maintaining admixture ofvaporized essential oil with the chlorinated solvent vapor during theexposure of the metal parts to the solvent and of the solvent to theatmosphere or to moisture.

6. An improved process of treating greasy objects with hot volatileorganic chlorinated grease solvents that decompose when exposed in' thehot vapor state to the atmosphere or to moisture, and of preventingcorrosion of metal parts,

1 whether of the apparatus used or the objects being treated, that comein contact with such hot liquid or vaporous solvent, notwithstanding theexposure of the solvent; which process comprises heating and vaporizing,along with the organic chlorinated solvent that is exposed to theatmosphere or to moisture, stabilizing essential oil and a stabilizingorganic base that imparts an alkaline reaction to the moist chlorinatedsolvent, both said essential oil and said organic base beingchlorinatable and also compatible with said chlorinated solvent,vaporizing with it without being decomposed by heat but not boiling 01!from it below the boiling point of said solvent; and treating theobjects with the solvent thus stabilized, while maintaining admixture ofvaporized essential oil and organic base with the chlorinated solventvapor during the exposure of the metal parts to the solvent and of thesolvent to the atmosphere or to moisture.

7. An oil and grease solvent composition, stabilized and adapted forcleaning or grease solvent use while hot under atmospheric exposure orwith moisture, and comprising volatile chlorinated hydrocarbon greasesolvent boiling under substantially 150 C., in combination withcompatible stabilizing essential oil and stabilizing organic base of theclass consisting of amines and of basic cyclic organic compoundscharacterized by nitrogen in the ring, coacting as a stabilizer for thesolvent, said essential oil and said organic base being volatile withthe solvent in the stated range and boiling sufliciently near theboiling point of the solvent to insure vaporization of the aforesaidcomposite stabilizer concurrently with the boiling of the solvent insubstantial proportion, the said composite stabilizer being present insumcient proportion to stabilize the solvent against decomposition inthe hot vapor state, and the said organic base in suflicient proportionto impart an alkaline reaction to the composition.

8. An oil and grease solvent composition, stabilized and adapted forcleaning or grease-solvent use while hot under atmospheric exposure orwith moisture, and comprising volatile chlorinated aliphatic hydrocarbongrease solvent boiling under substantially 150 C., in combination withcompatible stabilizing essential oil and stabilizing organic amine base,coacting as a stabilizer for the solvent, said essential oil and saidorganic base being volatile with the solvent in the i a I 10 bilized andadapted 1015018831118 or grease solvent I stated range andboilingsumciently near the boiling point of the solvent to insurevaporization oi the aforesaid composite stabilizer concurrently with theboiling of the solvent in substantial pr'oportion, the said compositestabilizer being present in sufllcient proportion to stabilize thesolvent j against decomposition in the hot vapor state,

and the said organic base in sumcient proportion to impart analkalinereaction to the composition; '9. Anoil andgrease solvent composition,Sta? use while hot under atmospheric exposure or with I moisture, andcomprisingvolatile chlorinated hydrocarbon grease solventboiling undersubstantially 150C in combination with compatible stabilizing essentialoil and stabilizing basic cyclic organic compound characterized bynitrogen; in:

the ring, coactingas a stabilizer for thesolvent.

'decompositionin the hot vapor state, and the said ba'sic cyclic organiccompound in sumci nt pr s portiontoimpart an alkaline reaction to thecom j position. I

s bilizedand adapted for cleaning or grease-solvent use while hot underatmospheric exposure or with 10. 'An oil and grease, solventcomposition, staaooeps'r rmoisture, and comprising volatile chlorinatedhydrocarbon grease solvent boiling under sub- 1 stantially 150C;, incombination with compatible stabilizing essential oil and a compatiblestabilizing pyridine, coacting as a stabilizer for the solvent, saidessential oil and said pyridine beng volatile with the solvent in thestatedrange and boiling 'suiliciently near the boiling/point oi thesolvent to insure vaporizationof the] aforesaid composite stabilizerconcurrently with the i boiling of the solvent in substantialproportion,

the said composite stabilizer being present in sub flcient proportion tostabilize the solventagainst decompositionin thehot vaporistate, and thesaid a pyridine in; sufllcient proportion to impart an alkaline'reactionto the composition. y I I 11. 'An oil and grease solvent composition,sta

bilized andadapted for cleaning or grease-solvent, i i use while hotunder atmospheric exposure or with'moisture, and comprisingtrlchlorethylene in a v I combination with compatibleatabilizlngegs fl I011 and pyridine, coacting as a stabilizer forthe trichlorethylene, saidessential oil,- as well as the a pyridine, boiling sumciently near theboiling point 5 Q g 'tion concurrentlywith the boilingoithe trichloraethylene, the said composite stabilizer being pres- 'ent in suflicientproportion to stabilize, the tri? chlorethylene against dccompofltion inthe hot vapor state, and the pyridine in sumcient' pro-' of thetrichlorethyiene to insure their vaporizaportion to impart an alkalinereaction to the composition;

